make sure the 'measure' span doesn't cause a scrollbar

Author: marijnh

lib/codemirror.js

@@ -20,7 +20,7 @@ var CodeMirror = (function() {
     // This mess creates the base DOM structure for the editor.
     wrapper.innerHTML =
       '<div style="position: relative">' + // Set to the height of the text, causes scrolling
-        '<pre style="position: absolute; visibility: hidden">' + // To measure line/char size
+        '<pre style="position: relative; height: 0; visibility: hidden; overflow: hidden;">' + // To measure line/char size
            '<span>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx</span></pre>' +
         '<div style="position: relative">' + // Moved around its parent to cover visible view
           '<div class="CodeMirror-gutter"><div class="CodeMirror-gutter-text"></div></div>' +